High RF Performance Enhancement-Mode Al2O3/AlGaN/GaN MIS-HEMTs Fabricated With High-Temperature Gate-Recess Technique

In this letter, we report high-performance enhancement-mode (E-mode) Al
₂
O
₃
/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated with high-temperature low-damage gate recess technique. The high-temperature gate recess is implemented by increasing the substrate temperature to 180 °C to enhance the desorption of chlorine-based etching residues during the dry etching of AlGaN barrier. High-crystal-quality Al
₂
O
₃
gate dielectric was grown by atomic-layer deposition using O
₃
as the oxygen source to suppress hydrogen-induced weak bonds. The fabricated E-mode MIS-HEMTs exhibit a threshold voltage of 1.6 V, a pulsed drive current of 1.13 A/mm, and very low OFF-state standby power of
$6.8 \times 10^{\mathrm {-8}}$
W/mm at
$V_{\mathrm {GS}} =0$
V and
$V_{\mathrm {DS}} =30$
V. At 4 GHz and in pulse-mode operation, the output power density and power-added efficiency were measured to be 5.76 W/mm and 57%, both of which are the highest for GaN-based E-mode MIS-HEMTs reported to date.